Habitat destruction a major cause of ancient extinction: study

A new study questions whether hunting is the primary driver of major drops in animal populations, suggesting that destruction of animal habitats through farming is a potentially bigger threat.

According to a study published Tuesday in the journal Scientific Reports, researchers found that farming was the key factor in the eradication of large mammals on the island of Madagascar.

The findings highlight that hunting is not the only way — “or perhaps even the main way” — that humans impact the wild animal populations around them, according to a statement from the Max Planck Institute of Geoanthropology, which carried out the research.

“Our results suggest that occupation and alteration of space, through the burning of forests for introduced grazing species, drove the extinction of large animals on the island, rather than the mere presence of hunters,” Sean Hixon, lead author of the paper, said in a statement.

To draw its conclusions, Planck Institute scientists examined the sudden extinction approximately 1,000 years ago of the massive island’s menagerie of large, unique reptiles, birds and mammals.

These now-extinct Madagascan creatures included gorilla-sized lemurs, 10-foot-tall elephant birds, grand tortoises and pygmy hippos for a thousand years.

Their disappearance had long been blamed on a combination of overhunting and climatic change, according to a statement from the institute.

But that fails to explain why animal populations stayed relatively stable for a thousand years of human habitation — between the arrival of the first settlers 2,000 years ago and the sudden extinctions around 1000 AD, as Mongabay reported.

The answer lies in the destructive role played by agriculture in spiking human populations and wiping out habitat, according to the researchers from the Planck Institute.

Populations of lemurs and elephant birds began to disappear from the fossil record at about the same time that traces of settled agriculture appear, according to the research team.

These include charcoal — a sign of the burning of forests to open up new fields — and the bones of domestic animals like zebu, cattle and dogs.

What killed off the hippos and grand tortoises was a vast human-architected act of landscape transformation, the researchers found. They concluded that human conversion of wild landscapes — which wiped out the green corridors between shrinking animal habitats, breaking up populations into small, fragmented islands — acted as a far larger threat.

The importance of maintaining those corridors — known in wildlife management as “habitat connectivity” — has become ever more important to the modern attempt to protect large animals from extinction, according to a fact sheet from the Center for Biological Diversity.

While U.S. populations of mountain lions, panthers, bears and elk have long lived alongside human fields and settlements, a new force has helped cut their habitats into disconnected pieces: cars, the center noted.

The bisecting of historic wildlife ranges by highways can lead populations into terminal decline, as newly separated populations succumb to inbreeding, birth defects and ultimately extinction — spreading further chaos throughout prey populations they once kept in check.

Southern California’s native cougars, for example, have begun to show serious birth defects caused by the slicing and dicing of their gene pools into tiny segments by the region’s proliferation of freeways, according to Scientific American.

That makes connecting those pools a key step in halting the decline of such populations — a move California has made on a grand scale. 

In April 2022, California Gov. Gavin Newsom (D) joined federal and local partners to break ground on an epic solution to that problem: the Liberty Canyon Wildlife Crossing, the world’s largest wildlife bridge, according to a statement.

The crossing will give cougars and other wildlife a safe means of crossing the deadly barrier of the 10-lane 101 Freeway — connecting cougar populations in the Santa Monica Mountains with those in the Simi Hills and Santa Susana Mountains, according to the state.